1. Field of the Invention
The invention relates to excavating machines and, more particularly, relates to a rock saw having a rotary cutting wheel and a conveyor assembly capable of conveying all excavated materials from the cutting wheel to a truck.
2. Discussion of the Related Art
It is often necessary to dig relatively narrow trenches (on the order of 3" to 2'), for receiving television cables, fiber optic cables, etc., through packed earth, asphalt, concrete, or even solid rock--materials too hard to be excavated by traditional chain type trenchers. Rock saws have proven to be ideally suited for this task. The typical rock saw includes a self-propelled chassis having a rock saw assembly extending from the rear end thereof which cuts a trench in the ground as the chassis is propelled forwardly. The rock saw assembly includes a hydrostatically powered carbide-tipped rotary cutting wheel which cuts through rock or other hard materials and throws excavated materials to the front of the cutting wheel. Rock saws of this type are disclosed in a brochure published by Bruff Manufacturing Limited, Worcestershire, England (the Bruff brochure) and in U.S. Pat. No. 5,381,616 to Disney. Similar rock saws are disclosed in Martin U.S. Pat. No. 4,542,940 and Martin U.S. Pat. No. 4,640,551.
All previously-known rock saws are incapable of conveying excavated materials away from the machine. The materials simply accumulate in front of and beside the cutting wheel such that, after trenching is complete, excavated materials are piled to either side of the trench. Discharging materials in this manner traditionally did not present a serious problem because excavated materials were simply used as backfill and thus need not be retrieved. However, government regulations and/or industrial requirements now frequently prohibit the use of the excavated materials for backfill. The loose excavated materials therefore must be retrieved and removed from the work site after the trenching operation is complete. This retrieval and removal are labor intensive and expensive. Moreover, if a "clean" trench, i.e., one which must be free of loose materials, is required, piling excavated materials beside the trench inevitably leads to some of the materials sliding back down into the trench either immediately after trenching or during the material retrieval process. In either case, loose materials must be cleaned out of the trench--usually manually--before the cable or pipeline can be laid.
The aforementioned problems could be remedied by discharging excavated materials from the cutting wheel directly onto a conveyor assembly. Other types of digging instruments such as chain trenchers have this capability because the digging implement also is capable of delivering materials to a laterally-extending conveyor which in turn delivers materials to a discharge conveyor assembly. However, rock saws merely throw excavated materials away from the cutting wheel rather than conveying them away from the trench and thus are poorly suited for use with traditional discharge conveyor assemblies, the inlet ends of which typically are not located close enough to the rock saw to receive materials thrown by the cutting wheel. Complete retrieval of essentially all materials excavated by a rock saw would require that the inlet end of the conveyor assembly ride on the ground in an excavated materials discharge region located immediately in front of the cutting wheel. The ideal conveyor assembly and rock saw assembly should also be versatile enough to assure material retrieval even after marked changes in trench depth. No previously known conveyor assembly or rock saw assembly has these capabilities.